Comparative Development of Embryos

Embryology is the study of how animals develop before birth. By studying embryos, scientists can find clues about how different species are related to each other.

For example, at the earliest stages, embryos of fish, birds, and mammals look so alike that it’s hard to tell them apart.

As they grow, some unexpected features appear. For example, these embryos develop tiny throat openings called gill slits, though they are not actual gills.

In fish and young amphibians, these develop into gills, allowing them to breathe underwater.

However, in mammals, the tissue from these slits forms parts of the jaw and middle ear bones.

These similarities suggest that all vertebrates evolved from a common ancestor that once had gills.

Take humans and chimpanzees, for example. We didn’t evolve directly from each other, but our embryos look alike, showing we shared a common ancestor before evolving into a separate species.